# Anthropic Claude Sonnet 4.5 API

> Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows. It delivers state-of-the-art performance on coding benchmarks such as SWE-bench Verified, with improvements across system design, code security, and specification adherence. The model is designed for extended autonomous operation, maintaining task continuity across sessions and providing fact-based progress tracking. Sonnet 4.5 also introduces stronger agentic capabilities, including improved tool orchestration, speculative parallel execution, and more efficient context and memory management. With enhanced context tracking and awareness of token usage across tool calls, it is particularly well-suited for multi-context and long-running workflows. Use cases span software engineering, cybersecurity, financial analysis, research agents, and other domains requiring sustained reasoning and tool use.

Source: https://www.sandbase.ai/models/anthropic/claude-sonnet-4.5
API reference: https://www.sandbase.ai/models/anthropic/claude-sonnet-4.5/docs

## Facts

- Provider: Anthropic
- Type: Language model
- Model ID: `anthropic/claude-sonnet-4.5`
- Price: $3 per 1M input tokens, $15 per 1M output tokens
- Context window: 200K tokens, up to 64K output tokens
- Capabilities: chat, vision, reasoning, structured output, function calling
- Billing: pay per use from one SandBase balance; no provider account or subscription needed

## Call it

- Chat Completions API: `POST https://api.sandbase.ai/v1/chat/completions`
- Messages API: `POST https://api.sandbase.ai/v1/messages`

```bash
curl -X POST https://api.sandbase.ai/v1/chat/completions \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "anthropic/claude-sonnet-4.5",
  "messages": [
    {
      "role": "user",
      "content": "Hello"
    }
  ],
  "max_tokens": 2048
}'
```

## FAQ

### How do I call Anthropic Claude Sonnet 4.5 through SandBase?

Create a SandBase API key, then send requests with the model ID "anthropic/claude-sonnet-4.5" to Chat Completions API (/v1/chat/completions) or Messages API (/v1/messages) at https://api.sandbase.ai. The request examples on this page show the exact payload.

### How much does Anthropic Claude Sonnet 4.5 cost?

$3 per 1M input tokens and $15 per 1M output tokens, billed per request from your SandBase balance. Discounts, when available, are shown in the pricing on this page.

### What is the context window of Anthropic Claude Sonnet 4.5?

200K tokens of context, with up to 64K output tokens per response.

### How does Anthropic Claude Sonnet 4.5 score on benchmarks?

Anthropic Claude Sonnet 4.5 scores 20.7 on the Artificial Analysis Intelligence Index (v4.3), ranking #62 of 83 models on SandBase; Coding Index 52.1, Agentic Index 15.8. Source: Artificial Analysis, measured as Claude 4.5 Sonnet (Reasoning).

### Which features does Anthropic Claude Sonnet 4.5 support?

Anthropic Claude Sonnet 4.5 supports vision (image input), reasoning, function calling, structured output. See Specifications above for the full list.

### Do I need a separate Anthropic account?

No. One SandBase API key and balance gives you access to Anthropic Claude Sonnet 4.5 and the other models in the catalog; you do not need to sign up with Anthropic separately.